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Useful Notes on the Mutation Theory for Evolution | Biology

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Read this articles to get information on mutation theory for evolution!

On the basis of the sudden changes in organisms. Hugo de Vries (1840-1935) proposed mutation theory for evolution. According to it mutation was the whole truth of evolution. Since mutations were known to be random, evolution was also considered to proceed at random. Many geneticists supported such a theory and they did not attach any importance, whatsoever, to the natural selection. They also thought that there are no adaptations, but only chance preadaptions.

Mutation theory of de Vries could explain some of the objections raised against Darwin’s natural selection theory. As opposed to Darwin’s hypothesis, de Vries attached importance to sudden changes or discontinuous variations, called “sports” by the former and “mutations” by the latter. On the basis of this, cases of overspecialization can be easily explained. One can also explain how the hereditary variations could originate and distinguish them from other environmental variations.

Considerable amount of work on frequency, nature, spectrum and size of mutations has been done in the modem times. It should be realized that hereditary changes can be brought about due to structural changes in chromosomes or due to changes at the genie level. These are called chromosomal mutations and gene mutations, respectively. Both kinds of changes play their roles in evolution. There are a large number of cases like Drosophila, Crepis, etc., where speciation has proceeded due to structural changes in chromosomes.

Hugo de Vries thought that mutations would always involve bigger and sudden changes. We now definitely know that the changes due to single mutation may vary from a major change, used for distinguishing species, genera or families to the changes which cannot be easily detected.

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The former are called systematic macro mutations, while the latter are micro mutations. Here, the cases are known where bigger mutations could be important, but in majority of the cases the smaller changes are more important. It is because if a genotype which is well adjusted into an environment, is too drastically altered it will not be able to adjust.

Minute changes, on the other hand, can be useful and help the organism to adjust in the new environmental conditions. Thus, mutation theory in its original form, as proposed by de Vries, does not hold good. However, evolution is a complex process and involves a complex set of factors. Mutation does play a very important role in evolution, but by no means is the only force working for organic evolution.